Relativistic effects in physics and chemistry of element 105. [Part] I.

A detailed study of the electronic structure and bonding of the pentahalides of group 5 elements V, Nb, Ta, and element 105, hahnium (and Pa) has been carried out using relativistic molecular cluster Dirac-Slater discrete-variational method. A number of calculations have been performed for different geometries and molecular bond distances. The character of the bonding has been analyzed using the Mulliken population analysis of the molecular orbitals. It is shown that hahnium is a typical group 5 element. In a great number of properties it continues trends in the group. Some peculiarities in the electronic structure of HaCl_5 result from relativistic effects.

Relativistic effects in physics and chemistry of element 105. [Part] II.

Relativistic self-consistent charge Dirac-Slater discrete variational method calculations have been done for the series of molecules MBr_5, where M = Nb, Ta, Pa, and element 105, Ha. The electronic structure data show that the trends within the group 5 pentabromides resemble those for the corresponding pentaclorides with the latter being more ionic. Estimation of the volatility of group 5 bromides has been done on the basis of the molecular orbital calculations. According to the results of the theoretical interpretation HaBr_5 seems to be more volatile than NbBr_5 and TaBr_5.

Relativistic effects in physics and chemistry of element 105. [Part] III.

Electronic structures of MOCl_3 and MOBr_3 molecules, where M = V, Nb, Ta, Pa, and element 105, hahnium, have been calculated using the relativistic Dirac-Slater discrete variational method. The character of bonding has been analyzed using the Mulliken population analysis of the molecular orbitals. It was shown that hahnium oxytrihalides have similar properties to oxytrihalides of Nb and Ta and that hahnium has the highest tendency to form double bond with oxygen. Some peculiarities in the electronic structure of HaOCl_3 and HaOBr_3 result from relativistic effects. Volatilities of the oxytrihalides in comparison with the corresponding pentahalides were considered using results of the present calculations. Higher ionic character and lower covalency as well as the presence of dipole moments in MOX_3 (X = Cl, Br) molecules compared to analogous MX_5 ones are the factors contributing to their lower volatilities.

Relativistic effects in physics and chemistry of element 105. [Part] IV.

Results of relativistic (Dirac-Slater and Dirac-Fock) and nonrelativistic (Hartree-Fock-Slater) atomic and molecular calculations have been compared for the group 5 elements Nb, Ta, and Ha and their compounds MCl_5, to elucidate the influence of relativistic effects on their properties especially in going from the 5d element Ta to the 6d element Ha. The analysis of the radial distribution of the valence electrons of the metals for electronic configurations obtained as a result of the molecular calculations and their overlap with ligands show opposite trends in behavior for ns_1/2, np_l/2, and (n -1 )d_5/2 orbitals for Ta and Ha in the relativistic and nonrelativistic cases. Relativistic contraction and energetic stabilization of the ns_1/2 and np_l/2 wave functions and expansion and destabilization of the (n-1)d_5/2 orbitals make hahnium pentahalide more covalent than tantalum pentahalide and increase the bond strength. The nonrelativistic treatment of the wave functions results in an increase in ionicity of the MCl_5 molecules in going from Nb to Ha making element Ha an analog of V. Different trends for the relativistic and nonrelativistic cases are also found for ionization potentials, electronic affinities, and energies of charge-transfer transitions as well as the stability of the maximum oxidation state.

Modeling and Analysis of Two-Part Type Manufacturing Systems

This paper presents a model and analysis of a synchronous tandem flow line that produces different part types on unreliable machines. The machines operate according to a static priority rule, operating on the highest priority part whenever possible, and operating on lower priority parts only when unable to produce those with higher priorities. We develop a new decomposition method to analyze the behavior of the manufacturing system by decomposing the long production line into small analytically tractable components. As a first step in modeling a production line with more than one part type, we restrict ourselves to the case where there are two part types. Detailed modeling and derivations are presented with a small two-part-type production line that consists of two processing machines and two demand machines. Then, a generalized longer flow line is analyzed. Furthermore, estimates for performance measures, such as average buffer levels and production rates, are presented and compared to extensive discrete event simulation. The quantitative behavior of the two-part type processing line under different demand scenarios is also provided.

Art i part :la figura del/la professional de l'educació social en processos de desenvolupament cultural comunitari

Anàlisi de la figura de l'educador/a social en processos de desenvolupament comunitari a partir d'experiències diverses a Catalunya

Les Metodologies docents i la seva valoració per part dels estudiants universitaris

Se analizan las preferencias de los estudiantes respecto al uso de determinadas metodologías y el grado en el que éstas son percibidas como facilitadoras del aprendizaje. Los participantes son estudiantes de una asignatura optativa de segundo ciclo de Psicología de la Universitat de Girona durante el curso 2008-2009. Los resultados indican que los estudiantes valoran favorablemente todas las metodologías docentes utilizadas a lo largo del curso. No obstante, la clase expositiva es la preferida y la que consideran más útil de caras al aprendizaje, por encima de otras metodologías más activas como pueden ser les clases interactivas, el role-playing, el análisis de casos clínicos, las lecturas de documentos y el trabajo por proyectos. Asimismo se observa una estrecha relación entre las preferencias de los estudiantes por un método y la valoración de éste como herramienta útil para el aprendizaje, aunque esta última valoración supera a la preferencia del estudiante por el mismo, en todos los casos. Trabajar en pareja es claramente la opción preferida por la mayoría de los estudiantes, frente al trabajo individual o en grupos más numerosos. No existe relación entre esta opción y la valoración que realizan de las diferentes metodologías como facilitadoras del aprendizaje o su preferencia por alguna de ellas. Se discuten los resultados en el marco de la renovación metodológica que propone el Espacio Europeo de Educación Superior y se sugieren acciones futuras para incrementar la comprensión de las motivaciones de los estudiantes

Dynamic bandwidth management as part of an integrated network management system based on distributed agents

We present a system for dynamic network resource configuration in environments with bandwidth reservation and path restoration mechanisms. Our focus is on the dynamic bandwidth management results, although the main goal of the system is the integration of the different mechanisms that manage the reserved paths (bandwidth, restoration, and spare capacity planning). The objective is to avoid conflicts between these mechanisms. The system is able to dynamically manage a logical network such as a virtual path network in ATM or a label switch path network in MPLS. This system has been designed to be modular in the sense that in can be activated or deactivated, and it can be applied only in a sub-network. The system design and implementation is based on a multi-agent system (MAS). We also included details of its architecture and implementation